Method of manufacturing semiconductor silicon single crystal wafer

ABSTRACT

A silicon wafer sliced from a silicon single crystal having a low oxygen concentration is used as an epitaxial substrate to provide semiconductor silicon single crystal wafers exhibiting good electrical characteristics at a low cost. A semiconductor silicon single crystal having a resistivity in a range of 0.005 to 0.02 Ω·cm and an oxygen concentration of 12×10 17  atoms/cm 3  (ASTM&#39;79) or less is manufactured by a Czochralski (CZ) method. The resulting silicon single crystal is shaped into a silicon single crystal substrate on which a silicon single crystal is epitaxially grown.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a method of manufacturing asemiconductor silicon single crystal wafer (hereinafter also referred tosimply as a "silicon wafer" or a "wafer"), and more particularly, to amethod of manufacturing a high quality epitaxial wafer which is requiredto improve electrical characteristics of the silicon wafer for use inmanufacturing highly integrated semiconductor devices.

2. Description of the Related Art

Conventionally, silicon single crystal wafers made from a silicon singlecrystal, for use in highly integrated and miniatuarized semiconductordevices, have been produced by a Czochralski method (hereinafter the "CZmethod") which is advantageous in manufacturing wafers of largerdiameters.

Since the method of producing a silicon single crystal according to theCZ method utilizes a quartz crucible, oxygen atoms dissolved into asilicon melt from the quartz crucible are trapped into a silicon singlecrystal while the crystal is grown.

Such oxygen atoms exist at interstitial positions in a silicon singlecrystal in a super saturation state, so that they are deposited to formbulk micro defects (BMD) during heat treatment steps in fabricatingsemiconductor devices. Since the semiconductor devices have electricalcircuits formed in the vicinity of a surface of the silicon singlecrystal wafer, BMD formed in such a region, if any, would cause problemssuch as a significant degradation of electrical characteristics such astime zero dielectric breakdown (TZDB) or the like.

To solve such problems, an intrinsic gettering (IG) heat treatment isgenerally used before a semiconductor device fabricating step as aparticular pre-heat treatment.

This is a heat treatment method which involves a high temperature heattreatment conducted to a silicon wafer containing interstitial oxygenatoms, manufactured by the CZ method, to reduce the interstitial oxygenconcentration on the surface of the silicon wafer through out-diffusionof the oxygen atoms therein, thereby forming a defect-free layer in thevicinity of the surface, and then heat treatment for oxygenprecipitation nuclei formation at a low temperature to form BMD withinthe wafer.

With this treatment, the surface of the wafer, which serves as asemiconductor device fabricating region, is defect free, and the BMDincorporated within the wafer serves as gettering sites for heavy metalimpurities during heat treatment steps or the like, thereby providing ahigh quality wafer.

However, in the recent increasingly highly integrated semiconductordevices, there are BMD remaining on the surface of the silicon waferafter the IG heat treatment due to an insufficient reduction ofinterstitial oxygen concentration, and a grown-in defect (see Semicond.Sci. Technol. 7, 1992, 135) introduced into a single crystal duringcrystal growth, which remains in the silicon single crystal wafer (seeJpn. J. Appl. Phys. Vol. 36, 1997 L591-594), thereby causing a problemof deteriorating electrical characteristics of the devices.

To solve these problems, in one method, a high quality semiconductorsilicon single crystal wafer is produced by epitaxially growing asilicon single crystal on a silicon single crystal wafer. The epitaxialgrowth essentially differs from growth of a single crystal by the CZmethod in the mechanism of growth. For example, when SiH₂ Cl₂ is used asa source gas, SiCl₂ molecules dissolved at high temperatures chemicallyadsorb to hollow bridge sites.

Then, as Cl₂ molecules are removed from the SiCl₂ molecules through asurface reaction with H₂ molecules, Si epitaxially and regularly growson the silicon single crystal wafer in a parallel state. Therefore,according to this method, there can be produced silicon single crystalwafers which are for fabricating high quality semiconductor devices andfree from micro-defects such as grown-in defects, without introducinggrowth striations in CZ crystal growth.

However, when a high interstitial oxygen concentration exists in asilicon single crystal wafer for epitaxial growth, interstitial oxygenatoms in the silicon single crystal diffuse into an epitaxial layer dueto a heat treatment during epitaxial growth to form defects (seeExtended Abstracts of The 42nd Spring Meeting, 28p-ZW-8, 1995, The JapanSociety of Applied Physics and Related Societies), sometimes resultingin deteriorated electrical characteristics of semiconductor devicesfabricated using such a silicon single crystal wafer.

While a manufacturing method has been proposed as measures taken againstthe above-mentioned problem by performing a high temperature heattreatment before epitaxial growth to reduce the interstitial oxygenconcentration of a silicon single crystal wafer, this proposed methodintroduces another problem of industrially increasing a cost due to theaddition of the heat treatment step.

OBJECT AND SUMMARY OF THE INVENTION

The present invention has been made in view of the problems inherent tothe prior art mentioned above, and its object is to provide asemiconductor silicon single crystal wafer exhibiting good electricalcharacteristics at a low cost by using a silicon wafer sliced from asilicon single crystal having a low oxygen concentration for anepitaxial wafer.

To solve the problems mentioned above, the present invention provides,in a first aspect, a method of manufacturing a semiconductor siliconsingle crystal wafer comprising the steps of producing a semiconductorsilicon single crystal having a resistivity in a range of 0.005 to 0.02Ω·cm and an oxygen concentration of 12×10¹⁷ atoms/cm³ (ASTM'79) or lessby a Czochralski method, shaping said silicon single crystal into asilicon single crystal wafer, and epitaxially growing a silicon singlecrystal on said silicon single crystal wafer.

Also, in a second aspect, the present invention provides a method ofmanufacturing a semiconductor silicon single crystal wafer comprisingthe steps of producing a semiconductor silicon single crystal having aresistivity in a range of 1 to 30 Ω·cm and an oxygen concentration of12×10¹⁷ atoms/cm³ (ASTM'79) or less by a Czochralski method, shapingsaid silicon single crystal into a silicon single crystal wafer, andepitaxially growing a silicon single crystal on said silicon singlecrystal wafer.

Preferably, the silicon single crystal is produced by a magnetic fieldapplied Czochralski (MCZ) method which is effective in reducing theoxygen concentration within a silicon single crystal, as disclosed inJapanese Patent Laid-open Publication No. 56-104791 and others.

In the present invention, while similar effects can be generated usingsilicon single crystals with a low oxygen concentration produced eitherby the CZ method or by the MCZ method, the production by the MCZ methodis more effective for providing silicon single crystals with a lowoxygen concentration.

Normal wafers typically used in the current semiconductor devicefabrication have the resistivity in a range of 1 to 30 Ω·cm, whilewafers expected to generate effects of gettering and a measure againstthe latch-up with a high doping concentration of boron have theresistivity in a range of 0.005 to 0.02 Ω·cm. The method according tothe present invention is applicable to wafers having either resistivity.

When MOS diodes fabricated using a wafer manufactured according to themethod of the present invention are evaluated for an oxide filmbreakdown characteristic, they exhibit good electrical characteristics.However, if MOS diodes are fabricated from a wafer sliced from asemiconductor silicon single crystal having an oxygen concentrationexceeding 12×10¹⁷ atoms/cm³ (ASTM'79), they exhibit degraded electricalcharacteristics.

A semiconductor silicon single crystal wafer of the present invention ismanufactured by the foregoing method according to the present invention,and exhibits good electrical characteristics such as an oxide filmbreakdown characteristic.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing electrical characteristics of MOS diodes inExamples 1 and 2;

FIG. 2 is a graph showing electrical characteristics of MOS diodes inExamples 3 and 4; and

FIG. 3 is a graph showing electrical characteristics of MOS diodes inComparative Examples 1 and 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be further described in connection withseveral manufacturing examples and practical examples. It goes withoutsaying that these examples only illustrates preferred specificimplementation of the present invention, and it should not be construedthat the present invention is limited to these specific examples.

MANUFACTURING EXAMPLE 1

110 kg of starting polysilicon chunks were charged in a quartz crucibleof 22".o slashed. in diameter, and boron was added to make a singlecrystal having a resistivity of 10 Ω·cm. An Ar gas was provided into agrowth furnace and a pressure therein was adjusted for removing foreignsubstances of SiO evaporated from a silicon melt. The polysilicon chunkswere melted by a resistance heating element. Then, a seed crystal wasimmersed in the silicon melt, and the seed was rotated in thecounter-clockwise direction, while the crucible was rotated in theclockwise direction, at 6 rpm. Dislocation introduced into the seedcrystal due to thermal stress was eliminated in a necking step, and asilicon single crystal having a diameter of 200 mm (8".o slashed.) wasgrown by the CZ method. An oxygen concentration was measured for thissilicon single crystal by the Fourier transformation infraredspectroscopy (FT-IR) and shown in Table 1. It should be noted that themeasured value of oxygen concentration in Table 1 was the value measuredin conformity to ASTM'79.

MANUFACTURING EXAMPLE 2

A silicon single crystal having a diameter of 200 mm was grown undersimilar conditions to those of Manufacturing Example 1 except that boronwas added to make a single crystal having a resistivity of 0.012 Ω·cm inanother batch process for growing a low resistivity crystal. An oxygenconcentration was measured for this silicon single crystal by the gasfusion analysis method (GFA) and shown in Table 1.

COMPARATIVE MANUFACTURING EXAMPLE 1

For comparison, a silicon single crystal was grown under conditionssimilar to those of Manufacturing Example 1 except that 150 kg ofpolysilicon chunks were charged in a quartz crucible of 24".o slashed.in diameter, and boron was added to make a single crystal having aresistivity of 10 Ω·cm. An oxygen concentration was measured for thissilicon single crystal by FT-IR and shown in Table 1.

COMPARATIVE MANUFACTURING EXAMPLE 2

A silicon single crystal was grown under similar conditions to those ofComparative Manufacturing Example 1 except that boron was added to makea single crystal having a resistivity of 0.012 Ω·cm. An oxygenconcentration was measured for this silicon single crystal by GFA andshown in Table 1.

                                      TABLE 1                                     __________________________________________________________________________                 Crucible                                                                           Polysilicon                                                                              Oxygen                                             Pulling Diameter    Charge Resistivity Concentration                          Method    ("φ)    Amount (kg)   (Ω · cm) (×10.s                                 up.7 atoms/cm.sup.8)                             __________________________________________________________________________    Manufacturing                                                                        CZ Method                                                                           22   110   10.00                                                                              10.60                                              Example 1                                                                     Manufacturing CZ Method     22        110         0.012           12.00       Example 2                                                                     Comparative  CZ Method    24        150         10.45           14.56                                     Example 1                                         Comparative  CZ Method     24        150         0.011           14.75                                    Example 1                                       __________________________________________________________________________

MANUFACTURING EXAMPLE 3

150 kg of starting polysilicon chunks were charged in a quartz crucibleof 24".o slashed. in diameter, and boron was added to make a singlecrystal having a resistivity of 10 Ω·cm. The MCZ method was employedwith a horizontal magnetic field generator disposed around a growthfurnace. An Ar gas was provided into a growth furnace and a pressuretherein was adjusted for removing foreign substances of SiO evaporatedfrom a silicon melt. The polysilicon chunks were melted by a resistanceheating element. A horizontal magnetic field was applied to the melt ata strength of 4000 G (gauss) at the center of the melt. Then, a seedcrystal was immersed in the silicon melt, and the seed was rotated inthe counter-clockwise direction, while the crucible was rotated in theclockwise direction, at 1.3 rpm. Dislocation introduced into the seedcrystal due to thermal stress was eliminated in a necking step, and asilicon single crystal having a diameter of 200 mm (8".o slashed.) wasgrown. An oxygen concentration was measured for this silicon singlecrystal by FT-IR and shown in Table 2. It should be noted that themeasured value of oxygen concentration in Table 2 was the value measuredin conformity to ASTM'79.

MANUFACTURING EXAMPLE 4

A silicon single crystal was grown under similar conditions to those ofManufacturing Example 3 except that boron was added to make a singlecrystal having a resistivity of 0.012 Ω·cm in another batch process forgrowing a low resistance crystal. An oxygen concentration was measuredfor this silicon single crystal by GFA and shown in Table 2.

                                      TABLE 2                                     __________________________________________________________________________                 Crucible                                                                            Polysilicon                                                                                  Oxygen                                        Pulling Diameter    Charge  Resistivity Concentration                         Method    ("φ)    Amount (kg)    (Ω · cm) (×10.                                 sup.7 atoms/cm.sup.8)                            __________________________________________________________________________    Manufacturing                                                                         MCZ  24   150   10.52                                                                              11.80                                              Example 3                                                                     Manufacturing   MCZ       24        150         0.012           11.84                                     Example 4                                       __________________________________________________________________________

EXAMPLE 1

A silicon single crystal produced in Manufacturing Example 1 wassubjected to cylindrical grinding, slicing, lapping and polishing stepsto obtain wafers. A silicon single crystal was epitaxially grown on eachof the wafers in a thickness of 6 μm. The respective epitaxial layerswere adjusted to have a resistivity of 12 Ω·cm.

For artificially simulating heat treatment processes in thesemiconductor manufacturing, CMOS heat treatments at 1000° C. for fourhours (in dry O₂ atmosphere); 1150° C. for 13 hours (in N₂ atmosphere);and 1000° C. for six hours (in dry O₂ atmosphere) were applied to theabove-mentioned epitaxial wafers. Each of the wafers applied with thesetreatments were cleaned, and subjected to gate oxidization to form anoxide film of 10 nm in thickness, thus fabricating polysilicon gate MOSdiodes.

These MOS diodes were evaluated and counted as good chips in the casewhere they each exhibited an electrical characteristic that electricalfield applied to the oxide film was 10 MV/cm or more when a currentdensity applied through the oxide film was 1 mA/cm² under conditionsthat the area of the gate electrode was 8 mm², a current density indecision was at 1 mA/cm², and the number of measured diodes was 100chips per wafer. The number of good chips was divided by the totalnumber of evaluated diodes to derive a value which was used as a C-modeyield (good chip yield) for evaluating the electrical characteristic.

This example (high resistivity, CZ method and low oxygen concentrationarticles) exhibited the C-mode yield of 92% on the average, thusexhibiting extremely good electrical characteristics. For the evaluationof the electrical characteristics, two wafers were used for eachexample. The C-mode yield resulting from this example is shown in FIG. 1together with the C-mode yield of Example 2 (low resistivity, CZ methodand low oxygen concentration articles) described below.

EXAMPLE 2

A silicon single crystal produced in Manufacturing Example 2 was used tofabricate polysilicon gate MOS diodes in a manner similar to Example 1,and similarly evaluated for the electrical characteristic. This example(low resistivity, CZ method and low oxygen concentration articles)exhibited the C-mode yield of 86% on the average, thus indicating goodelectrical characteristics. The C-mode yield resulting from this exampleis shown in FIG. 1 together with the C-mode yield of Example 1 (highresistivity, CZ method and low oxygen concentration articles) describedabove.

EXAMPLE 3

A silicon single crystal produced in Manufacturing Example 3 were usedto fabricate polysilicon gate MOS diodes in a manner similar to Example1, and similarly evaluated for the electrical characteristics. Thisexample (high resistivity, MCZ method and low oxygen concentrationarticles) exhibited the C-mode yield of 83% on the average, thusindicating good electrical characteristics. The C-mode yield resultingfrom this example is shown in FIG. 2 together with the C-mode yield ofExample 4 (low resistivity, MCZ method and low oxygen concentrationarticles) described below.

EXAMPLE 4

A silicon single crystal produced in Manufacturing Example 4 was used tofabricate polysilicon gate MOS diodes in a manner similar to Example 1,and similarly evaluated for the electrical characteristics. This example(low resistivity, MCZ method and low oxygen concentration articles)exhibits the C-mode yield of 87% on the average, thus indicating goodelectrical characteristics. The C-mode yield resulting from this exampleis shown in FIG. 2 together with the C-mode yield of Example 3 (highresistivity, MCZ method and low oxygen concentration articles) describedabove.

COMPARATIVE EXAMPLE 1

A silicon single crystal produced in Comparative Manufacturing Example 1was used to fabricate polysilicon gate MOS diodes in a manner similar toExample 1, and similarly evaluated for the electrical characteristic.This comparative example (high resistivity, CZ method and high oxygenconcentration articles) exhibited the C-mode yield of 68% on theaverage, thus indicating the degraded electrical characteristic. TheC-mode yield resulting from this comparative example is shown in FIG. 3together with the C-mode yield of Comparative Example 2 (lowresistivity, CZ method and high oxygen concentration articles) describedabove.

COMPARATIVE EXAMPLE 2

A silicon single crystal produced in Comparative Manufacturing Example 2was used to fabricate polysilicon gate MOS diodes in a manner similar toExample 1, and similarly evaluated for the electrical characteristic.This comparative example (low resistivity, CZ method and high oxygenconcentration articles) exhibited the C-mode yield of 58% on theaverage, thus indicating significantly degraded electricalcharacteristics. The C-mode yield resulting from this comparativeexample is shown in FIG. 3 together with the C-mode yield of ComparativeExample 1 (high resistivity, CZ method and high oxygen concentrationarticles) described above.

As is apparent from the results of measuring the electricalcharacteristics of the foregoing Examples 1-4 and Comparative Examples1-2, the silicon single crystals with a lower oxygen concentration incrystal (Examples 1-4) exhibit good characteristics, i.e., the C-modeyield generally exceeding 80% associated with the oxide film breakdownstrength, whereas the silicon single crystals containing oxygen in highconcentration (Comparative Examples 1-2) exhibit the C-mode yieldapproximately from 55 to 70%. It is therefore revealed that goodelectrical characteristics can be ensured by epitaxially growing asilicon single crystal on a silicon wafer having a low oxygenconcentration as shown in Examples 1-4, whereas the electricalcharacteristics are degraded when a silicon single crystal isepitaxially grown on a silicon wafer having a high oxygen concentrationas shown in Comparative Examples 1-2.

As described above, the present invention is advantageous in thatsemiconductor silicon single crystal wafers exhibiting the goodelectrical characteristics can be manufactured at a low cost.

Obviously various minor changes and modifications of the presentinvention are possible in the light of the above teaching. It istherefore to be understood that within the scope of the appended claimsthe invention may be practiced otherwise than as specifically described.

What is claimed is:
 1. A method of manufacturing a semiconductor siliconsingle crystal wafer comprising the steps of:producing a semiconductorsilicon single crystal having a resistivity in a range of 0.005 to 0.02Ω·cm and an oxygen concentration of 12×10¹⁷ atoms/cm³ (ASTM'79) or lessby a Czochralski method; shaping said silicon single crystal into asilicon single crystal wafer; and epitaxially growing a silicon singlecrystal on said silicon single crystal wafer.
 2. A method ofmanufacturing a semiconductor silicon single crystal wafer according toclaim 1, wherein said silicon single crystal is produced by a magneticfield applied Czochralski method.
 3. A semiconductor silicon singlecrystal wafer having good electrical characteristics manufactured by amethod of manufacturing a semiconductor silicon single crystal waferaccording to claim
 2. 4. A semiconductor silicon single crystal waferhaving good electrical characteristics manufactured by a method ofmanufacturing a semiconductor silicon single crystal wafer according toclaim
 1. 5. A method of manufacturing a semiconductor silicon singlecrystal wafer comprising the steps of:producing a semiconductor siliconsingle crystal having a resistivity in a range of 1 to 30 Ω·cm and anoxygen concentration of 12×10¹⁷ atoms/cm³ (ASTM'79) or less by aCzochralski method; shaping said silicon single crystal into a siliconsingle crystal wafer; and epitaxially growing a silicon single crystalon said silicon single crystal wafer.
 6. A method of manufacturing asemiconductor silicon single crystal wafer according to claim 5, whereinsaid silicon single crystal is produced by a magnetic field appliedCzochralski method.
 7. A semiconductor silicon single crystal waferhaving good electrical characteristics manufactured by a method ofmanufacturing a semiconductor silicon single crystal wafer according toclaim
 5. 8. A semiconductor silicon single crystal wafer having goodelectrical characteristics manufactured by a method of manufacturing asemiconductor silicon single crystal wafer according to claim 4.